13test02：信用卡校验

/*#include<iostream>

using namespace std;

void input();

int counter=0,jishu_sum=0,oushu_sum=0,sum=0;

int input_num[20];

int main()

{

cout<<"Please enter 16 to 19 numbers which arrange from 0~9:,input 'e' means end";

cout<<endl;

input();

cout<<"Inputed numbers is: "<<endl;

for(int i=0;i<counter;i++)

cout<<input_num[i];

int jishu_i=counter;

int oushu_i=counter;

do

{





jishu_sum+=input_num[jishu_i];

jishu_i-=2;

}

while(jishu_i>=0);

do

{

int oushu=input_num[oushu_i-1]*2;

if(oushu>9) oushu-=9;

oushu_sum+=oushu;

oushu_i-=2;

}

while(oushu_i>=0);





sum=oushu_sum+jishu_sum;

if(!(sum%10))

cout<<endl<<"The card numbers is ligal."<<endl;

else 

cout<<endl<<"The card numbers is illigal."<<endl;





return 1;

}

















void input()

{

char end;

do

{   if(counter<20)





{   cin>>input_num[counter];

while(input_num[counter]>9)

{

cout<<"error,please enter numbers from 0~9:";

cin>>input_num[counter];

}

cout<<"end?";

cin>>end;

    cout<<counter+1<<" numbers have been inputed"<<endl<<"please enter numbers from 0~9"<<endl;

   ++counter;

}





else 

{

cout<<"input again:";

counter=0;

input();

}





}while(end!='e');

}*/

#include<iostream>

using namespace std;

int input(char*);

int sum1(char*,int);

int main()

{

char buffer[30]={'0'};

int numbers=input(buffer);

int sum=sum1(buffer,numbers);//不要让函数名与变量名相同.

if(sum%10==0)cout<<"ligal;"<<endl;

else cout<<"illigal:"<<endl;

return 0;

}

















int input(char*p)

{

cout<<"请输入16至19位0～9的数字:"<<endl;

int i=0;

do{

if(i==30)break;

p[i]=(char)getchar();//getchar()返回值是读取字符对应的ASCII值。

//可以将其强制转化为char类型

//cout<<p[i];


}while(p[i++]!='\n');





if(i<17||i>20)

{

cout<<"位数输入错误，请重新输入:"<<endl;

input(p);

}

else cout<<"the card number:"<<p<<endl;

return i;//函数可以返回局部变量但是不能返回局部指针.

}









int sum1(char* p,int x)

{

int oushu_sum=0,jishu_sum=0;

for(int i=x-1;i>=0;i-=2)

jishu_sum+=p[i];

for(i=x-2;i>=0;i-=2)

{

if(p[i]*2>=10)

oushu_sum+=p[i]*2-9;

else oushu_sum+=p[i]*2;

}

return oushu_sum+jishu_sum;

}





/*int main()

{

cout<<100-'a';//计算机对字符常量的处理是将其翻译为对应的ASCII值

              //虽然肉眼看到的是‘a',但是计算机执行的时候看到是其码值.

















}*/